1. Field of the Invention
This invention relates to a primer composition, and more particularly a primer composition effectively used in adhesion of silicone rubber.
2. Description of the Prior Art
In recent years, with expansion of purposes for which silicone rubbers are used, it has been required to adhere silicone rubber to various materials as exemplified by metals and synthetic resins, and various primer compositions used in adhesion of silicone rubbers have hitherto known in the art. For example, known as a primer composition for use in a silicone rubber curable by addition reaction is a composition comprising a mixture of an organosilicon compound having an alkoxy group with an organosilicon compound having an SiH group (Japanese Patent Publication (KOKOKU) Nos. 2107/1986, 4865/1986 and 4866/1986).
Meantime, because of excellent thermal resistance, silicone rubbers are often used in a severe atmosphere as in high-temperature air, high-temperature water vapor, or high-temperature oil. In the instance where the silicone rubber adhered to a substrate through the above primer composition is used in such a severe atmosphere, the silicone rubber may be peeled from the substrate because of a lowering of the adhesion attributable to the primer at the adhesion interface between it and the substrate, before the silicone rubber itself deteriorates. In particular, when immersed in a high-temperature silicone oil, because of the swell of silicone rubber, a stress is applied to the interface between the silicone rubber and substrate to produce a strain, and this strain causes the peeling, or the adhesion may be abruptly lowered in instances in which the primer composition contains a component soluble in the silicone oil.